Farmer's-style tomato sauce with seasonal garden vegetables is rustic Italian cooking at its best. A vegetarian mediterranean sauce that's healthy, fresh, and ideal for family dinners.
Heat the olive oil in a large heavy-bottomed pan over medium-low heat. Add diced onion and cook gently for 5 minutes, stirring often, until translucent but not browned.
Stir in chopped carrot and celery. Continue to cook for 6–7 minutes, maintaining medium-low heat to sweat the vegetables without scorching, until they're beginning to soften.
Add diced zucchini, chopped eggplant, and red bell pepper. Raise heat to medium, and cook another 8 minutes, stirring to prevent sticking, until all vegetables are just tender.
Pour in the canned tomatoes (crushed by hand or with a spoon), then add dried oregano, salt, and black pepper. Mix well, increase heat to medium-high until just bubbling, then immediately reduce to a low simmer.
Simmer uncovered for 35–40 minutes, stirring every 10 minutes, until the sauce thickens and vegetables are soft but not falling apart. Turn off the heat, stir in torn basil leaves, and adjust seasoning to taste before serving.